The present invention is directed to integrated circuits and their processing for the manufacture of semiconductor devices. More particularly, the invention provides techniques for removing photolithographic films without substantial modifications to conventional equipment and processes. Merely by way of example, the invention has been applied to the manufacture of advanced integrated circuit devices, but it would be recognized that the invention has a much broader range of applicability.
Integrated circuits have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Conventional integrated circuits provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of integrated circuits.
Increasing circuit density has not only improved the complexity and performance of integrated circuits but has also provided lower cost parts to the consumer. An integrated circuit or chip fabrication facility can cost hundreds of millions, or even billions, of U.S. dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of integrated circuits on it. Therefore, by making the individual devices of an integrated circuit smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as each process used in integrated fabrication has a limit. That is to say, a given process typically only works down to a certain feature size, and then either the process or the device layout needs to be changed. Additionally, as devices require faster and faster designs, process limitations exist with certain conventional processes and materials.
An example of such a process is removal of photolithographic films (such as anti-reflective films) using conventional techniques. In conventional techniques, wet etching typically does not completely remove anti-reflective films, particularly DUO™ Bottom Anti-Reflective Coatings by Honeywell International Inc (“DUO”). FIGS. 1A-1C are a simplified illustrations of a conventional process for removing photolithographic films from a wafer 100. Wafer 100 includes a photoresist film 102, anti-reflective film 104, and a fluorine doped silicate glass (FSG) layer 106. In this example, photoresist film 102 and anti-reflective film 104 are used in a photolithographic process to form a trench 110 in FSG layer 106. The resulting trench 110 can be used as a via with a bottom copper trace 108. After the formation of trench 110 (or other features), photoresist layer 102 is removed using a dry ash process as shown in FIG. 1B. The dry ash process includes a wafer temperature of greater than 250 degrees Celsius in an oxygen atmosphere. Next, as illustrated in FIG. 1C, a wet etch process is performed to remove anti-reflective layer 104. Unfortunately, anti-reflective layer 104 is only partially removed. These and other limitations may be found throughout the present specification and more particularly below.
From the above, it is seen that an improved technique for processing semiconductor devices is desired.